Carbon Dioxide Detected on Exoplanet HD 189733b

[/caption]The Hubble Space Telescope has detected carbon dioxide on a planet orbiting another star. The star in question is HD 189733 (also known as V452 Vulpeculae, a variable star designation), a binary system over 60 light years away, and the planet is approximately the size of Jupiter (called HD 189733b). The exoplanet is already known to contain water and methane molecules from previous Hubble and Spitzer campaigns, but this is the first time CO2 has been discovered.

But why all the fuss? CO2 is another chemical marker for the existance of life. But HD 189733b isn’t a candidate planet for the search for life. After all, this “hot Jupiter” will not be hospitable to the development of even the most basic lifeforms (life as we know it in any case). This discovery is ground-breaking in that CO2can be sensed on a planet many light years from Earth…
“The carbon dioxide is kind of the main focus of the excitement, because that is a molecule that under the right circumstances could have a connection to biological activity as it does on Earth,” said Mark Swain of NASA’s Jet Propulsion Laboratory. “The very fact that we’re able to detect it, and estimate its abundance, is significant for the long-term effort of characterizing planets both to find out what they’re made of and to find out if they could be a possible host for life.”

Indeed, it wasn’t only carbon dioxide that was found; carbon monoxide was also detected in the exoplanet’s atmosphere. But the fact that CO2 is a “tracer” for life and it has been detected on a planet other than a planet known to contain life (Earth) is incredibly significant. As time goes on, observation techniques advance, it is hoped small rocky bodies will be observed. If this can be done, an Earth-like planetary survey can be carried out.

Earth atmospheric molecules detected by Venus Express (ESA)

In fact, ESA’s Venus Express was recently used to characterize what Earth looks like from a distant vantage point, providing astronomers and future extraterrestrial hunters with a model that can be used when observing distant star systems. If a planet, with a similar chemical composition to that of the Earth is discovered, it would become a prime candidate for harbouring alien life.

So how did Hubble detect CO2 on HD 189733b? Through a spectroscopic analysis of the infrared radiation being emitted by the hot planet, Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) spotted an abundance of CO and CO2. Certain molecules in the exoplanet’s atmosphere absorb certain wavelengths of infrared light, leaving a spectroscopic “fingerprint” in the light detected by Hubble.

This kind of campaign is best carried out on star systems with their ecliptic plane seen edge-on to the Earth. This means the orbit of the exoplanet carries it behind the parent star and then infront of it. HD 189733b transits (or eclipses) its parent star every 2.2 days and then orbits behind the star. This is an ideal situation as astronomers are able to measure the emission from the star (when the line of sight to the exoplanet is blocked by the star) and use those measurements to subtract from spectroscopic analysis of the exoplanet. This technique isolates the exoplanet emission making it possible to analyse the chemical composition of its “day-side” atmosphere.

“We’re starting to find the molecules and to figure out how many of them there are to see the changes between the day side and the night side,” Swain said.

All these developments by Hubble will aid the future of exoplanet studies. In 2013, NASA’s James Webb Space Telescope will be launched to look out for “super-Earth” exoplanets (i.e. rocky planets larger than Earth), observing in near-infrared wavelengths. Therefore, the carbon dioxide discovery in the atmosphere of HD 189733b helps astronomers refine techniques to detect yet another tracer for life…

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By Ian O'Neill
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[Check out my space blog: Astroengine.com]
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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!

24 Responses

“We live in times of wonder Simon says” … To Astrofiend … I’m a Trekker and I agree with that statement.Unless there’s some unexpected new discovery we won’t be whizzing to the stars anytime soon. But of course we are, in a way, using Hubble. The significance of these discoveries needs to be constantly reiterated less they are lost in a sea of fuzzy thinking. Anyway, many Trekkers know that show is about our modern way of life. The stardrive is just a convenient story telling device.

Carbon based life, not lifeforms in general. I keep wondering why are we only looking for carbon based lifeforms? Even through earth only harbors carbon based life, that’s only one example- for all we know we are the minority type of lifeforms.

Even then what are we going to do if we find life?- Calculate the abundance of life in the universe? What we need is some better resolution so we might be able to pick up more in depth details, like orbiting structures, wartime explosions, mass movement, radiation, something that should result from civilization – a little more important, even if they breath methane and their planet is inhospitable to us, at least then we could interact with them.

All that aside we as a whole should concentrate more on becoming space faring, before seeing a place that we can’t even get to.

Some people just aren’t happy. Yes, we should be looking for more chemicals and for life markers of lifeforms whose metabolism we know nothing about. We should also forego telescopes and just warp out to these planets and look at them. Better yet, we should hop through a wormhole and just be there.

Right now we are doing incredible science with the devices, techniques, and knowledge that we have. Each discovery and each technical advance moves our abilities further out. Someday, we will be able to identify every type of molecule that exists on each asteroid around every star and we will be able to communicate with every form of intelligent life that is out there. Unil then, I am fascinated and thankful for the science being done right now. Just a few years ago, we couldn’t even prove that other stars had planets. Now we are examining atmosheres on exoplanets.

Some people are just never happy with anything. Quit carping and enjoy the wonders our scientists are uncovering for us.

If you want to learn about what are required for life-forming molecules to form, i recommend you study some Molecular Biology. Carbon based life forms will be the dominant form, because very few, if any, other base can sustain the complexity needed.

What you want, may not be the same as i want, or what others want. I hope that you realise you are only speaking for yourself, and definitely not for me.

“All that aside we as a whole should concentrate more on becoming space faring, before seeing a place that we can’t even get to.”

Flaming Pope – we will never, in our lifetime, or the next generations or the two or three after that, be able to harness enough energy to get a manned mission to even the closest stars. The problems involved are simply too great. In fact, I doubt it would be technically possible to have a manned mission travel beyond Mars orbit in our lifetimes without a simply ungodly amount of resources being poured into it, and Mars is over 100,000 times closer than the very nearest star at it’s furthest from the Earth.

Unfortunately, perhaps for us, being able to ‘see a place we can’t even get to’ is the best we can ever realistically hope for. I think it nothing short of a miracle that we are able to find out so much about such places without being able to physically visit them. Losing out on such profound discoveries for some Space Trek pipe dream would be simply laughable.

Odds are, it is simply a matter of time before we find many Earth-sized planets. When this happens of course, research priorities will undoubtedly shift towards a full-scale assault on studying the atmospheres of such planets, and I think the next generation of space telescopes will be optimised for just that purpose.

I would say ‘that’ll be an exciting time in astronomy’, but really when isn’t it an exciting time in astronomy!

Think from the 1950’s up until now and think of the tech.thats been invented, now think 50 years from now its hard to predict another explosion of such groundbreaking inventions I feel we’ve reached a bottle neck a kind of writers block in inventions. What we need is another revolutionary mode of transporting ourselves, something with more bang for the buck…

If the search for life outside our own are to be taklen seriously it should definately pay extra attention to similarities with our own planet, including chemistry. One reason may be that all life may be similar to terrestrial ones, but of course this is controversial and may or may not be true. More important: If such a scientific programe should make any sense, one must know what to look for.
The alternative could easily be searching “something” or “anything”. A bit vague, is´nt it?

I agree absolutely with Marco. The science being done is fantastic and we should celebrate that not continually carp about how fuzzy the images are; how did they forget to put that on the mission; are they hiding something?; why can’t we see this, that or the other?; have they considered this? For goodness sake people ten years ago most, if not all, of what we’re seeing was barely imagined.

Great article. Suggestion for a future article. It would be great to have a brief synopsis of the history behind planet (and chemical signature) detecting–how it evolved, techniques developed, technology that made it possible, and so forth.

It wasn’t so long ago (at least I can remember) when the best thinkers out there were wondering if there even were exoplanets. I think that’s about as close to a modern day renaissance as you can get!

Dutch Delight, there’s always a possibility, but I’d say that for this planet (and this planet type), the probability of having moons at all of any significant size is just about zero. That close to the star, the Hill Sphere is so small, even for a big planet and a small star, that the likelyhood of having moons within it wouldn’t be great to start with, and if you add the perturbing effects in the moon’s orbits of having a huge mass so close, in all likelyhood nothing other than possible temporary captures would be orbiting hot jupiters.

And, in any case, spectral line strength depends on the quantity the given molecule is present in. And in anything short of a double planet, you’d always get a whole lot more atmosphere in the planet than in its eventual satellites. So it’s safe to assume that most, if not all, of that spectrum comes from the planet itself.

Life is extremely complicated – it must carry out all sorts of metobolic processes. Only carbon has a chemistry that is complex enough to support living systems. No other element comes even close. Therefore both CO2 and methane (CH4) can be considered markers for the possibility of life. Both are commonplace throughout the solar system and universe as a whole.

“”We live in times of wonder Simon says” … To Astrofiend … I’m a Trekker and …”

I’ve got nothing against Trekkers or anything… I enjoy an episode from time to time. I simply used it as a convenient example of the type of spacefaring that is so far beyond anything we’re currently capable of that investigation through science is literally the only way we may come to learn about these far away places. It was simply the counterpoint to Flaming Pope’s view as I understood it.

Don’t get me wrong though – I think humanity has a fighting chance of one day becoming spacefaring in that sense, but we’d be talking at least hundreds of years even before manned missions beyond the Earth-Moon system become somewhat commonplace.

“Flaming Pope – we will never, in our lifetime, or the next generations or the two or three after that, be able to harness enough energy to get a manned mission to even the closest stars. The problems involved are simply too great. In fact, I doubt it would be technically possible to have a manned mission travel beyond Mars orbit in our lifetimes without a simply ungodly amount of resources being poured into it, and Mars is over 100,000 times closer than the very nearest star at it’s furthest from the Earth.”

Don’t be so sure about manned flight beyond Mars. The scientists and engineers of the original Project Orion (the nuclear pulse Orion, not today’s wimpy Apollo-on-steroids) in the late 50’s/early 60’s, expected manned flight to Saturn to be possible as soon as 1970…

It was not technical or engineering issues that stopped that vision, it was the Test Ban Treaty. Other kinds of nuclear propulsion are possible (and we once did have ground-based nuclear thermal rockets, but after the first Moon landings, support for plans to get to Mars in the 1980’s dried up…and the NERVA program was cancelled, as there was little point in funding an engine without a mission, either), once we become less fearful saying of this other ‘n-word.’ (rational thought seems to stop whenever either one is uttered.)

I disagree, that our engineering and technology capabilities are ready for space travel! We do have an long way to go in that department. Beside all that, the most important factor is HUMANITY! That alone
is stopping us from going anywhere! Our life
span is limited under the current technological posibilities! Untill we are able to travel at light speeds, we have the human factor as a limitation!